Just switched to a macbook pro and it wants to delete everything on my iphone

This is very frustrating. I just got a macbook pro and I transfered everything in iTunes to my new computer using an external hard drive. I authorized iTunes on the new computer and connected my iPhone to sync it, but it wants to delete everything on my iPhone to replace it with the exact same files, but i fear all of my apps will have their data wiped and i will have to organize them into folders all over again. Is there any easy way to sync my iphone without first erasing everything on it? I'm sure this has been discussed before but the information is surprisingly hard to find.

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